Yohji Uchiyama

Life-cycle assessment of electricity generation options: The status of research in year 2001

Abstract This article presents the environmental impacts of electricity generation systems, based on life-cycle assessments (LCAs). These assessments normally include impacts from extraction, processing and transportation of fuels, building of power plants and generation of electricity. The LCAs show that the following options have an excellent performance: hydropower (run-of-river and with reservoir), nuclear energy and windpower. Hydropower with reservoir does have high land requirements, but in spite of this, it is possible to conclude that it has the highest performance, if we consider 2 factors not always included in LCAs: firstly, reservoirs can provide secondary benefits such as irrigation or flood control; and secondly, hydropower has a high operating flexibility that can improve the reliability of electricity supply.

Present efforts of saving energy and future energy demand/supply in Japan

Past and future trends of Japanese energy demand/supply are investigated in industry, residential and commercial and transportation sectors. Recent growth of the energy demand is getting stable by rapid change of industrial structure from materials and heavy industries to service industries. However, the Japanese long-term energy outlook reports one percent per year of energy demand until 2010 because of moderate energy growth of households, services and transportation. It is inevitable to reinforce energy saving and expanded utilization of alternative energy sources such as natural gas, nuclear power and renewable energy in order to achieve the CO2 emission of the government target up to 2010. The paper also describes expectable measures to reduce energy consumption in each sector, and to clarify life cycle CO2 emissions of electric power generating technologies which could mitigate CO2 emissions.

Derivation of energy-embodiment functions to estimate the embodied energy from the material content

The embodied energy includes the direct and indirect energy consumed for the entire production process. These values are needed to estimate impacts on energy consumption due to changes in consumption patterns. We have developed a model of the economic system to account for every production process. This model illustrates interrelations among production processes by incorporating sectors that produce multiple products. The model is consistent with available input-output coefficients and the material flow in each process. By exploring our model, we derived energy-embodiment functions that evaluate the embodied energy of an arbitrary product in terms of material content.

Estimating the embodied carbon emissions from the material content

The embodied carbon emissions includes the direct and indirect carbon emitted for the entire production process. These values are needed to estimate impacts on carbon emissions due to changes in consumption patterns. We have developed a model of the economic system to account for every production process. This model illustrates interrelations among production processes by incorporating sectors that produce multiple products. At each multiple product-producing sector, inputs differ in accordance with the material content of the output product. The model is consistent with available input-output coefficients and the physical law of material flow in each process. By exploring our model, we derived carbon embodiment functions that evaluate the embodied carbon emissions of an arbitrary product in terms of material content. Empirical analysis has been fulfilled using the available 405-sector input-output table of Japan.

Study on GHG control scenarios by life cycle analysis — World energy outlook until 2100 —

Abstract World energy supply up to the year 2100 has been analysed from a life cycle standpoint of the full fuel cycle. Five scenarios are set up and these scenarios are analysed and compared with regard to excess energy requirements, carbon emissions, health risks and investment costs for entire power generation systems. The current trend (fossil fuel-intensive) scenario of these scenarios is attractive from an investment standpoint, but deleterious froman environmental and risk standpoint. The CO2 removal and carbon recycle scenarios must get over the hard barriers of reducing excess energy use and investment costs through future technological innovations. Renewable energy technologies are environmentally appropriate and the renewable-intensive scenario could be introduced with acceptable cost burdens in long-term projections. The nuclear-intensive scenario is attractive from its economic, environmental and risk aspects, but must make efforts to acquire public and political acceptability for further worldwide adoption.

Seawater desalination using reusable type small PWR

Demand for seawater desalination is increasing, especially in regions such as the Middle East and North Africa, where populations are growing at a high annual rate. If such demand is met by fossil fuel energy, the influence on the environment, such as global warming, cannot be disregarded. Since these regions are behind in their preparedness of social capital infrastructure, such as power transfer grids, small reactors are considered to be more suitable for introduction than the large reactors found commonly in developed countries. Therefore, a small reusable PWR with mid-range pressure and temperature services, which does not require on-site refuelling, was devised for seawater desalination. In a small reusable PWR, spent fuel is taken out together with the reactor vessel and refuelled on the exterior fuel exchange base prepared independently. Thus, the safeguards against nuclear proliferation increase at a plant site because the lid of the reactor vessel is never opened at the site, in principle. The reactor vessel will be transported from the plant site to a fuel exchange base under stipulated conditions within a transportation cask after a long (about six years) operation. Since fuel handling facilities at the site become unnecessary through centralisation at a fuel exchange base, initial plant construction costs are reduced. In addition, the reactor vessel is reused until its service life has expired. This examination was based on the marine reactor of the experimental nuclear ship, Mutsu, after it had been applied for land use: at a lowered, midrange pressure and temperature service, in theory. It is possible to produce fresh water through reverse osmosis (RO) membrane pressure–rising seawater by a steam turbine driven pump. Using the method of driving a desalination unit high-pressure pump directly by low-pressure steam generated from the heating reactor, fresh water can be produced efficiently. Furthermore, operating at reduced pressure makes it possible not only to improve the transport performance of the reactor vessel but also to save plant construction costs, thus reducing bill materials of the primary system. There has been a worldwide trend for the RO method to be used for seawater desalination. So the reverse osmosis method was examined using low-pressure steam generated from a small heating reactor and compared with electrical power and evaporation methods (MED or MSF) utilising low-pressure steam towards a sea area with high salt concentration and countries that have been familiar with evaporation methods by fossil fuel energy.

Evaluation for the Adoption of Renewable Energy in China using Geographic Information System

AbstractRenewable energy is one of effective measures to decrease GHG emission. Its installed potential should be evaluated in a specific area, because renewable energy is a local energy. Especially, biomass energy should be evaluated in a region, because it has a wide geographical distribution. High costs for transportation, feedstock, and energy conversion are obstacles to promote the utilization of biomass energy sources. In this study, usable biomass potential and locations of biomass power plants are estimated by using Geographic Information System (GIS) and an optimal method in Guangdong Province. From the model analysis, we can obtain an optimal transportation process and the number of profitable conversion plants for woody biomass resource. In the optimal case, the installed biomass power plants are five units with the range of power capacity from 23.5 to 43.5 [MW], and its total annual power generation is 1135.5—1228.8 [106kWh/yr] in Guangdong.

Comparative analysis of embodied liabilities using an inter-industrial process model: gasoline- vs. electro-powered vehicles

We developed a model of economy-wide production systems by incorporating a material balance concept into the standard input-output framework. This inter-industrial process model represents the physical flow of materials throughout the industrial network and thus is able to address the entire process involved with the production of a target product according to its material content. The model, which is based on some physically allowable assumptions, was calibrated using the available input-output coefficients for aggregated processes (sectors). We used detailed data on environmentally hazardous emissions and labour requirements for each sector to analyse the liabilities of substitutable products in terms of different factors, origins, and stages of the inter-industrial process network. To empirically examine the model, we applied it to analyse the production of a popular gasoline-powered vehicle and an electro-powered vehicle.

Analysis of the Clean Development Mechanism Considering the Environmental Co-benefits of Reducing Air Pollutants in China

An electricity generation planning model of the six major Chinese power grids was developed based on the General Algebraic Modeling System to evaluate and analyze the CDM (clean development mechanism), including consideration of the environmental co-benefits of reductions in air pollutants (SOx, NOx and particulate matter) achieved by advanced electricity generation technologies incorporating CCS (carbon capture and storage). An objective function was developed that included revenue from sales of electric power, total system cost, the cost of CO2 transport and storage, and emissions reduction co-benefits for SOx, NOx, and particulate matter. The objective function was minimized using an optimization model. We also developed a method for evaluating and analyzing the potential for transferring advanced power generation technologies into the Chinese power system through the CDM. We found that: (1) thermal power generation is predominant in the Chinese electricity system and will remain so for a long time; (2) advanced thermal plants are being installed as a result of the CDM, which contribute to decreasing emissions of CO2 and other air pollutants; and (3) CCS projects have significant potential to reduce substantial and sustained CO2 emissions from the Chinese power and industrial sectors.

Evaluation of Potential Geographic Distribution for Large-Scale Photovoltaic System in Suburbs of China

Since China is the largest CO2 emitting country in the world, photovoltaic (PV) systems are expected to be widely installed to reduce CO2 emission. In general, available area for PV installation depends on urban area due to differences in land use and slope. Amount of electricity generated by a PV system also depends on urban area because of differences in solar irradiation and ambient temperature. The aim of this study is to evaluate the installation of large-scale PV systems in suburbs of China, taking these differences into consideration. We have used a geographic information system (GIS) to evaluate amounts of installation capacity of large-scale PV systems, electricity generated, and CO2 emission reduction by the installation capacity of large-scale PV systems in suburbs of Liaoning, Shanghai, Anhui, and Guangdong. In Liaoning, the amount of CO2 emission reduction by the installation capacity of large-scale PV systems was estimated to be the largest, 3,058 kt-CO2/yr, due to its larger amount of the installation capacity, 2439.4 MW, than the amount of the installation capacity in other regions.